How Much Fat, Protein, and Carbs Should You Be Eating?

First, we feared eating too much fat. Then, the pendulum shifted, and we started to eye carbs as the enemy. But what's the real deal?

Now, a global study published in The Lancet is challenging the notion that one necessarily needs to be worse than the other: Rather, it might be that eating too much or too little of the nutrients is the actual problem.

Researchers from McMaster University in Canada followed more than 135,000 people in 18 countries—from South America to Africa to China—for about seven years. After analyzing survey data about their diet and health, the researchers found that people who ate more than 68 percent of their total calories from carbohydrates were 28 percent more likely to die during the follow up than those who took in a lesser percentage of their calories from carbs.

While the researchers didn’t look into the specific types of carbs these people were eating, it’s safe to assume based on past research that a large chunk of those carbs are refined ones, like white bread and rice, says lead study author Mahshid Dehghan, MS.c., Ph.D., especially when you consider countries with higher levels of poverty.

The nutritional breakdown of carbs is important, since previous studies suggest that foods with a high glycemic index—meaning they spike your blood sugar faster, like refined carbs tend to do—can increase your risk for several chronic diseases, like obesity and diabetes, says Dehghan. So while we don't advise cutting your carbs, we do recommend the majority of them come from complex sources, like whole grains and vegetables.

Looking for some healthy ways to get more energy into your diet? Check out these easy food swaps:

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As for fat? It had the opposite effect. When people ate more fat, their risk of death during that time period decreased. In fact, those who ate roughly 35 percent of their calories from fat were 23 percent less likely to die during follow-up than people who only consumed 11 percent of their calories from fat.

This relationship held true when considering all kinds of fat, including saturated, monounsaturated, and polyunsaturated. But doesn’t fat make you fat? Not necessarily. In fact, eating reduced fat foods can lead to weight gain, some research suggests.

What Should Your Macronutrient Balance Look Like?

Think about it: When you go on an extreme kind of diet—say, a super low-fat one—the rest your calories have to come from somewhere, right?

“When you reduce one component of your diet, you replace it with something else,” says Dehghan. “When you reduce your total fat, by default, you replace it with refined carbohydrates.” The result? Loading up on processed foods—like breakfast cereals, soda, and white pasta—can easily lead to weight gain, which spikes your risk for serious health issues, such as heart disease.

The reverse is possible when you go super high-fat and low-carb too, popularized by the ketogenic diet. When you don't eat enough carbs, your energy levels might crash, since they're your body's main source of fuel.

“We are not supporting very low carb or very high fat diets," says Dehghan. “We are saying that reducing your carbs is likely beneficial when [your intake] is already high.”

She adds that the purpose of their study is to present new evidence to add to the ongoing discussion of what a healthy diet should look like. Based on their specific findings, people should aim to eat 50 to 55 percent of their calories from carbs and roughly 35 percent from fat to reduce their risk of premature death, says Dehghan.

The study didn't specifically look at protein, which, along with carbs and fat, is vital in considering your macronutrient breakdown. So we decided to compare the study's recommendations for carbs and fat percentages to what the current Dietary Guidelines for Americans advises—while zeroing in on its recommended protein allowance, too.

The dietary recommendations from the study actually aren't so far off: The U.S. Dietary Guidelines say 45 to 65 percent of your calories should come from carbohydrates, while 20 to 35 percent should come from total fat. You should also get 10 to 35 percent of your calories from protein.

We checked in with Jim White, R.D., owner of Jim White Fitness Studios, to see if we could break all this down. Based on everything we learned, for the average guy looking to stay healthy, what should his macronutrient breakdown really be?

Shoot for 50 percent carbs, 30 percent protein, and 20 percent fat, he recommends, which seems to be a happy medium based on recommendations listed above. Making slight adjustments to your protein, carbs, and fat, won’t make a huge difference in results if you’re keeping your overall calories in check, he says. (Find out how many calories you need here.)

But if you have certain goals—say, you’re looking to build muscle or lose weight—then you may want to include more protein, but 35 percent is the highest White recommends. Then, you can adjust your fat and carbs accordingly. (In need of great recipes that will help you get there? Check out the Metashred Diet from Men's Health.)

Bottom line: No matter your personal macro ratio—which you can find here—pay attention to the nutritional breakdown of the foods you’re eating. And when you go lower in one nutrient, note what you’re replacing those missing calories with. It could make all the difference in your health.

Alisa HrusticAssociate EditorAlisa Hrustic, an associate editor at Prevention, has spent her entire career interviewing top medical experts, interpreting peer-reviewed studies, and reporting on health, nutrition, weight loss, and fitness trends for outlets like Women’s Health and Men’s Health, where she both interned and worked full-time.

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